Failing to Obtain Keg Carbonation in Beer

[doug293cz]

I suggest setting up a keg of IPA on a 50-foot PVC beer line, and doing some sensory analysis. I can probably get to this in the next month or so if people think it’s the right approach.

I'd rather see DO data from a properly designed and conducted experiment.

Brew on

 

[AlexKay]

I'd rather see DO data from a properly designed and conducted experiment.

Brew on

Ultimately, sensory results are what you’re concerned with. With a little critical thinking, one could come up an experiment with a suitable tasting panel and statistical analysis of results. Properly.

But DO is fine, as long as you can agree beforehand on what amount of DO difference would be significant, and have a meter with the appropriate sensitivity.

 

[Bobby_M]

Ultimately, sensory results are what you’re concerned with. With a little critical thinking, one could come up an experiment with a suitable tasting panel and statistical analysis of results. Properly.

But DO is fine, as long as you can agree beforehand on what amount of DO difference would be significant, and have a meter with the appropriate sensitivity.

Actually I'm more concerned with the raw oxygen data. I think you were suggesting that oxygen may not/probably doesn't get into the beer through the CO2 lines. If I'm mistaken and you actually meant that oxygen does make it into the beer through the CO2 lines but not to a level of sensory detection, correct me.

 

[doug293cz]

It’s an interesting argument. I’m not sure at all that interface kinetics will be a minor effect. We’re not at equilibrium here, and my intuition is that kinetic factors are going to be very important.

What matters is if the interface kinetics are anywhere near as slow as the diffusion kinetics. The diffusion kinetics definitely matter, but he diffusion kinetics will be pretty much identical for both lines. If the interface kinetics are more than an order of magnitude faster than the diffusion kinetics (the usual situation), then they won't make a significant difference, even if they are different for the two cases. I need to see some evidence that the interface kinetics are slow enough to matter. Intuition doesn't cut it.

Not being at equilibrium is a red herring. The conditions that matter are very nearly identical for the beer and gas lines, as discussed previously.

Some digging on the internet comes up with the “dual mode sorption” model, which seems to find application (though there are newer approaches) in describing gas diffusion through polymers. There’s a Langmuir-like term, and applications with multiple penetrants absolutely include competition for sites within the material.

Since we have the same gases competing for sites in the two cases, the effects of competition are going to be the same for both cases, so site competition won't drive a different behavior for the two cases.

Brew on

 

[DuncB]

Ok. Who has a DO meter?

I do, not used it yet though.

Only sensitive enough to work out whether my wort is oxygenated enough as it's ppM not ppB.

I like this interpretation of Mike Soltys line calculator as well.

https://www.brewingcalculators.com/beer-line-length/
I played around with the final gravity and it doesn't seem to make much of a difference between 1.012 and 1.003, but erring on a little longer but slower is better than waiting on a quick pour full of foam to settle and then it's flat.

Have to say adding in a keg of Saison at 3 vols has been challenging and added to the beer line chaos in the beer fridge.

 

[DuncB]

Maybe I should divert all of the ferment gas from my beer into the beer fridge, then I'll displace some oxygen and reduce the diffusion.

A practical use of a wasted gas!!

 

[AlexKay]

No, I’m going to stick with the position that transport of CO2 from solution into the polymer is not the same as transport from the gas phase. The relevant timescale to get CO2 from the liquid to the gas or vice versa, as the folks who do set-and-forget carbonation know, is multiple days.

If your intuition is that interface kinetics don’t matter, I’m willing to look at evidence you have on that point.

Anyway, I’m glad we’ve moved on from the proposition that positive pressure of CO2 can’t affect the transport of oxygen through the tubing. (At least I hope we’ve moved on. If we’re still stuck there I can try to provide dual mode sorption references once I’m not typing on my phone.)

Incidentally, I asked a draft system designer I know if the industry worried about O2 coming through gas lines, and got a resounding “nope.” He says red Bevlex 200 (vinyl) is the industry standard. Of course, much more product moves in a commercial application, so this doesn’t necessarily apply for homebrew.

 

[sibelman]

In the absence of evidence/data, we take anti-oxygen measures that are easy and cheap like replacing gas lines. There is some reason to suspect this could be beneficial, even though hard (or any!) data aren't available. And even though the intuitions of educated, articulate, experienced people vary considerably. Fun discussion though. Cheers!

 

[Bobby_M]

Incidentally, I asked a draft system designer I know if the industry worried about O2 coming through gas lines, and got a resounding “nope.” He says red Bevlex 200 (vinyl) is the industry standard. Of course, much more product moves in a commercial application, so this doesn’t necessarily apply for homebrew.

There are a lot of people bouncing around in their profession that don't really go too much further than "this works fine" for their entire careers. I'm just saying that it's not the final word on the topic by any means. No commercial account that is turning over a half barrel of bud light (another industry standard) in a weekend is going to complain that their customers tasted a bit of oxidation. Half the consumers of such beers have no problem pumping air into a keg on the deck for 8 hours.

I personally hate opaque 5/16 and 3/8" ID bevlex for two reasons. One is that it's unnecessarily oversized for what it's doing. Two, if you get beer backed up into the lines, you'd never know it.